Objective:To explore the causes and precaution procedures of olfactory dysfunction after transsphenoidal surgery for pituitary lesions.Methods:The clinical data of 72 patients underwent transsphenoidal surgery for pituitary lesions in our hospital from November 2016 to May 2018 were summarized. Resection under microscope was performed in 27 patients and resection under endoscope in 45 patients. The olfactory function of patients with postoperative olfactory disorders was evaluated one and 6 months after surgery. Bilateral nasal passages were examined by nasal endoscopy 3-6 months after surgery. Whether intraoperative operations were related to olfactory impairment was analyzed.Results:There were seven hyposmic/anosmic patients; three patients (6.7%) were operated via endoscopic approach and four patients (14.8%) were operated via microscopic transsphenoidal approach; incidence of olfactory dysfunction between the two groups showed no statistical difference ( P>0.05). One month after operation, two patients had a slight decrease in olfactory function, 4 had a severe decrease in olfactory function and one had anosmia. Six months after the operation, two patients with severe hypoxia got improvment, but failed to return to normal level; and the rest of the patients showed no significant improvement. Three-6 months after operation, nasal endoscopic examination found that all patients had healed nasal wound, two patients had large volume of nasal mucus secretion, and 3 patients had postoperative nasal mucosa adhesion. In these 72 patients,cauterization of the mucosa around the sphenoid ostium was performed in 6 patients, placement of the speculum above the sphenoid ostium was performed in 2 patients, and olfactory damage was noted in all the 8 patients. Conclusions:Olfactory dysfunction after transsphenoidal surgery for pituitary lesions is common, and attention should be paid.Placement of the speculum above the sphenoid ostium and cauterization of the mucosa around the sphenoid ostium might be the main reasons for olfactory damage.